JOHNSTON, Iowa — Newt Gingrich chided his GOP presidential opponents in a new TV ad for going negative and said separately Thursday that his checkered personal history wouldn't be to blame if he begins losing voter support in the run-up to Iowa's caucuses.

In an interview taped for Iowa Public Television, Gingrich said there will be some volatility in the polling ahead of the Jan. 3 precinct caucuses — the first votes of the GOP nominating contest — because of the attacks he's being subjected to on the airwaves.

"If you look at the amount of negative ads being run in Iowa by my opponents, I would be very surprised if we didn't see some ups and downs over the next three weeks," he said.

Rival Mitt Romney's latest attempt to sully Gingrich has been to cast him as an unreliable leader. Ron Paul, Michele Bachmann, Rick Perry and Rick Santorum also have stepped up their criticism as Gingrich has surged here and in other states.

Perry's campaign piled on Thursday with a new television ad in Iowa that casts both Gingrich and Romney as Washington insiders lacking conservative credentials. Perry is portrayed as an outsider in an attempt to make the struggling candidate more appealing to voters who have had it with career politicians being in charge in Washington.

"Gingrich and Romney. Insiders," a voice says in the spot, adding that Perry's plan to create jobs and overhaul Washington "make him the outsider political insiders fear most."

In his latest ad, Gingrich said voters want to hear politicians offer solutions for the nation's problems, not personal attacks.

"These are challenging and important times for America. We want and deserve solutions," Gingrich said in the ad running in Iowa, trying to stay above the fray while still poking at his opponents. "Others seem to be more focused on attacks rather than moving the country forward. That's up to them."

Gingrich didn't name any of his rivals but it's clear he was referring to them.

Romney and his allies have unleashed an aggressive effort to derail Gingrich during campaign events, media interviews and independent advertising.

Despite the attacks, Gingrich said Thursday that he has surged ahead because voters are looking past his troubled personal history for a candidate who has had big achievements. Some of Gingrich's rivals have tried to exploit his confessions of marital infidelity, three wives and ethical problems while representing Georgia in Congress.

"I think voters have rendered judgment and they understand my weaknesses and they understand my strengths," Gingrich said. "They believe that at a time when the country is in deep trouble they want somebody who has big solutions and somebody who has a track record of getting big things done."

Gingrich said that as House speaker he balanced the federal budget and overhauled welfare, and that those accomplishments outweigh his negatives.

He added that he's comfortable with voters getting to know him and said they have accepted his explanations of his past personal misconduct.

"It's a balanced judgment and I'm very open to people getting to know me and getting to understand me," Gingrich said. "Part of it is that people accept the sincerity of my willingness to talk about my life."

Thursday's campaign flurry came hours before six of the candidates were to meet in Sioux City for a debate sponsored by Fox News Channel and the Iowa Republican Party, their final such meeting before the Jan. 3 caucuses.

With time running short, Romney's campaign redoubled efforts to cast Gingrich as an unreliable leader on a host of fronts, including in statements and web videos.

One such video showed an old clip of Gingrich praising Romney and saying: "Gov. Romney in his business career created more jobs than the entire Obama Cabinet combined, so he could actually talk about it."

In a statement, Romney himself chastised Gingrich for calling Rep. Paul Ryan's Medicare plan, which is popular among many conservatives, "right-wing social engineering." Romney also pointed to a comment Gingrich made last week to the "Coffee & Markets" podcast, where he said: "If there's a program which is very, very unpopular, should Republicans impose it? And my answer is no! When we passed welfare reform, 92 percent of the country favored it, including 88 percent of people on welfare. (Ronald) Reagan ran to be a popular president, not to maximize suicide."

Romney argued that Gingrich was calling Ryan's plan "suicide" and added: "I know it can be popular with some people to use extreme language, but we're talking about the presidency of the United States."

Romney's campaign on Thursday highlighted support from a group of former Reagan administration officials, although many of the names had been previously announced.

The announcement was a jab at Gingrich, who has begun been selling himself as a "Reaganite." After a candidates' debate last week, Gingrich's campaign immediately issued a statement declaring, "Newt Gingrich claims the Reagan mantle."